Field of the Invention
The devices of the present disclosure relate generally to fluid injection systems for supplying fluids during medical and therapeutic procedures and, more specifically, for controlling the fluid supplied during an angiographic injection procedure.
Description of Related Art
In many medical diagnostic and therapeutic procedures, a physician or other person injects a patient with a fluid. In recent years, a number of injector-actuated syringes and powered injectors for pressurized injection of fluids, such as contrast media, have been developed for use in procedures such as angiography, computed tomography, ultrasound, and NMR/MRI. In general, these powered injectors are designed to deliver a preset amount of contrast media at a preset flow rate. Angiography is used generally in the diagnosis and therapeutic treatment of abnormalities in blood vessels. In an angiographic procedure, a radiographic image of vascular structure is obtained through the use of a radiographic contrast medium, sometimes referred to simply as contrast, injected through a catheter. The vascular structures are injected and filled with contrast. X-rays passing through the region of interest are absorbed by the contrast, causing a radiographic image of the blood vessels. The resulting images can be displayed on, for example, a monitor and recorded.
In a typical angiographic procedure, a physician places a catheter into a vein or artery. The catheter is connected to either a manual or to an automatic contrast injection mechanism. A typical manual contrast injection mechanism includes a syringe in fluid connection with a catheter. The fluid path also includes, for example, a source of contrast fluid, a source of saline, and a pressure transducer to measure patient blood pressure. In a typical system, the source of contrast is connected to the fluid path via a valve, for example, a three-way stopcock. The source of saline and pressure transducer P may also be connected to the fluid path via additional valves. The operator of the manual system manually controls the syringe and each of the valves to draw saline or contrast into the syringe and to inject the saline or contrast into the patient through the catheter connection.
The operator of the syringe may adjust the flow rate, or simply known as flow, and volume of injection by altering the force applied to the plunger of the syringe. Manual sources of fluid pressure and flow used in medical applications, such as syringes and manifolds thus typically require operator effort that provides feedback of the fluid pressure/flow generated to the operator. The feedback is desirable, but the operator effort often leads to fatigue. Thus, fluid pressure and flow may vary depending on the operator's strength and technique.
Automatic contrast injection mechanisms typically include a syringe connected to a powered injector having, for example, a powered linear actuator. Typically, an operator enters settings into an electronic control system of the powered injector for a fixed volume of contrast material and a fixed rate of injection. In many systems, there is no interactive control between the operator and the powered injector, except to start or stop the injection. A change in flow rate in such systems occurs by stopping the machine and resetting the parameters. Automation of angiographic procedures using powered injectors is discussed, for example, in U.S. Pat. Nos. 5,460,609, 5,573,515, and 5,800,397.
U.S. Pat. No. 5,800,397, for example, discloses an angiographic injector system having high pressure and low pressure systems. The high pressure system includes a motor-driven injector pump to deliver radiographic contrast material under high pressure to a catheter. The low pressure system includes, among other things, a pressure transducer to measure blood pressure and a pump to deliver a saline solution to the patient as well as to aspirate waste fluid. A manifold is connected to the syringe pump, the low pressure system, and the patient catheter. A flow valve associated with the manifold is normally maintained in a first state connecting the low pressure system to the catheter through the manifold, and disconnecting the high pressure system from the catheter and the low pressure system. When pressure from the syringe pump reaches a predetermined and set level, the valve switches to a second state connecting the high pressure system/syringe pump to the catheter, while disconnecting the low pressure system from the catheter and from the high pressure system. However, the arrangement of the system components of U.S. Pat. No. 5,800,397 results in relatively large amounts of wasted contrast and/or undesirable injection of an excessive amount of contrast when the low pressure, typical saline system, is used.
Unlike manual injection systems, however, there is little if any feedback to the operator of system pressure in the systems disclosed in the U.S. patents identified previously. There are potential advantages to such feedback. In the use of a manual syringe, for example, excessive back pressure on the syringe plunger can provide evidence of occlusion of the fluid path.
While manual and automated injectors are known in the medical field, a need generally exists for improved fluid injection systems adapted for use in medical diagnostic and therapeutic procedures where fluids are supplied to a patient during the procedure. A specific need generally exists for an improved fluid injection system for use in fluid injection procedures, such as angiography. Moreover, a continuing need exists in the medical field to generally improve upon known medical devices and systems used to supply fluids to patients during medical procedures, such as angiography, computed tomography, ultrasound, and NMR/MRI.